The invention relates generally to apparatus and a method of reducing the emissions of a diesel engine and, more specifically, to the use of low-proof hydrous alcohol fuels in a modified diesel engine for reducing the polluting emissions of the engine.
Internal combustion emissions are the primary cause of air pollution in many cities and metropolitan areas. Such emissions include uncombusted hydrocarbons, hydrocarbons formed in the combustion process, sulfur oxides, nitrogen oxides, and particulate matter. To attempt to reduce the quantities of these emissions, the federal and state governments have imposed emission standards. These standards typically apply to new engines, but have also been applied on a fleet-average basis to include previously manufactured engines in the emission reduction strategy. Over time, the standards have required lower and lower levels of emissions. New standards have been proposed to take effect in the next several years that will further significantly reduce the level of emissions that will be permitted of diesel engines widely used in the trucking and mass transit industries. There have, accordingly, been many and diverse attempts to reduce the levels of emissions, both of newly manufactured engines and of previously manufactured engines, through modification and add-on equipment programs.
Hydrocarbon emissions are undesirable because of the role they play in air pollution and also because they represent an energy loss from that available in the hydrocarbon fuel used in the engine. Sulfur oxides not only participate in local air pollution, including photochemical smog, but also are the principal cause of acid rain. Urban smog is caused primarily by nitrogen oxides (NOX). The black smoke of diesel engine exhaust is typically caused by particulate emissions which add to local air pollution and may cause health problems, including cancer, known to be caused by the polycyclic aromatic compounds in the solvent organic fraction of the particulates.
The levels of emissions of an engine are interrelated by complex and poorly understood mechanisms. It is known, for example, that adding anhydrous alcohol to gasoline will actually increase the hydrocarbon content of the fuel, but will also tend to reduce the levels of emitted particulates and carbon monoxide. Increasing the temperature of the in-cylinder combustion will usually result in more complete combustion of the fuel, and so reducing hydrocarbon emissions, but will result in an increase in nitrogen oxides and affect the polycyclic aromatic hydrocarbon constituents of the particulates. Sulfur oxide emissions can be reduced by using low-sulfur fuels, but it is known that reducing sulfur in the fuel normally changes the aromatics and boiling range of the fuel, both of which affect the amount of particulates emitted.
Many attempts have been made to improve engine efficiencies and reduce emissions, including the use of a hydrous alcohol supplemental fuel. In U.S. Pat. No. 4,708,118, a radically modified internal combustion engine, having three valves per cylinder, employed an injector to deliver a combination liquid and vapor fuel. A hydrous methanol mixture was added to the fuel in the intake manifold to lower the temperature of combustion and thereby reduce nitrogen oxide emissions. No teaching is provided in the patent as to the ratio of water to alcohol, or proof of the water/methanol mixture or of the timing amount of the hydrous methanol fuel used in the engine. Neither is there any direct control over the availability of the hydrous methanol to the engine.
U.S. Pat. No. 4,385,593 teaches a mixture of water and an unspecified alcohol that is heated to a gaseous state and mixed in the intake manifold with the gasoline and air mixture from the carburetor. The hydrous alcohol fuel is described to increase the mileage by as much as 10-20 percent. The patent teaches such fuel mixtures only for use with carbureted gasoline engines.